Study Of Localized Surface Plasmon Enhanced Ultraviolet Light-emitting Device Based On ZnO/SiO₂ Core/Shell Nanowire Array

Zn O, a wide band-gap semiconductor(3.37 e V) which has high exciton binding energy of 60 me V, is much easier to achieve excitonic emission at high temperature.It also has other advantages such as: abundant reserves and easily preparation, etc, and is considered to be an ideal candidate to replace Ga N material for developing ultraviolet light-emitting devices. However, it is known to us that the difficulties of preparing high quality p-Zn O repeatedly hamper the development of Zn O-based homojunction. Aiming for making the best of the excellent properties of Zn O material without the limitation in p-type doping, we turn to building Zn O-based heterojunction light-emitting. Comparing with the flat thin film structure, nano-structure become a research hotspot because of its gradually expanding demand and application. In the richly colorful nano-structure,one-dimensional Zn O nanowire arrays which has many great characters, such as high single crystal, excellent carrier transport and optical properties can enhance the efficiency of the device. In addition, metal localized surface plasmon, with high spatial localization property and strong local-field enhancement property, is confirmed to be an effective way to improve the performance of the device recently. Therefore, based on the construction of pure Zn O nanowire arrays pn heterostructure light-emitting diode, we introduce Ag nanoparticles localized surface plasmon to Zn O/Si O2 core/shell structure for constructing Ag localized surface plasmon enhance Zn O-based LED. Taking advantage of the resonant coupling effect between Ag nanoparticles localized surface plasmon and Zn O excitons, we can enhance the internal quantum efficiency and light extraction efficiency to achieve high performance light-emitting devices. The specific content is as follows:We combine the advantages of the nano-structure and metal localized surface plasmon and construct the Zn O/Si O2 core/shell structure on commercial p-Ga N by the low-cost hydrothermal synthesis and bionic polyelectrolyte layer by layer technique. And then, the Zn O nanowire arrays can be coated with different thickness of silica dielectric ranging from about 0 to 24 nm through adjusting the times of layer by layer technique. The result of SEM and TEM show the formation of the Zn O/Si O2 core/shell structure. In order to improve the efficiency of the device, we introduce Ag nanoparticles into the structure mentioned above. First, according to the condition of the resonant coupling effect between metal localized surface plasmon and Zn O excitons, we chose the Ag nanoparticles which diameter is about 10 nm for the devices. Subsequently, we discuss how the distinct dielectric spacer layer influence on the coulping resonance. Through experiment, we observe that when the Si O2 layer thickness is about 12 nm, the light-emitting device achieve a maximum of about 7-fold Zn O UV electroluminescence enhancement. In this case, the two contradictory factors: nonradiative energy transfer and charge transport process are all taken into account. Furthermore, by means of variable angel EL measurement, the spatial distribution of the Ag localized surface plasmon enhanced Zn O-based LED is extended evidently in comparison with bare Zn O nanowire array structure. This phenomenon is mainly attributed to its high spatial localization property and strong local-field enhancement property.